Guest network low signal - RAX50

My guest network has half the signal of my home network, and nothing can connect to it.

The problem is on all devices trying to connect.

Issue on both bands, 2.4ghz & 5ghz of guest network.

I've reset the router, renamed the SSID, turned guest network on & off again, changed channels, and tried connecting on different days. Most of the time the guest network doesn't even show up in the list of available networks because it's so slow.

What can I do to fix this?